An apparatus comprising a rotatable shaft extending through a housing bore may include one or more bearings and one or more rotary seal assemblies.
The bearings may support the shaft within the housing bore and/or transfer forces between the shaft and the housing.
The rotary seal assemblies may inhibit fluids and/or debris from transferring between an exterior of the housing and an interior of the housing.
In some such apparatus, the shaft may be capable of an amount of radial deflection within the housing bore and/or an amount of tilting within the housing bore.
Radial deflection of the shaft may result in the shaft becoming non-concentric with the housing bore as the shaft shifts radially within the housing bore. This non-concentricity of the shaft within the housing bore may negatively affect the performance of a rotary seal assembly.
Tilting of the shaft within the housing bore may result from radial deflection of a portion of the shaft, and may be accompanied by a bending and/or articulation of the shaft within the housing bore. Tilting of the shaft may be caused intentionally for the functioning of the apparatus, and/or may be the result of forces acting on the shaft during use of the apparatus. This tilting of the shaft within the housing bore may also negatively affect the performance of a rotary seal assembly.
In some apparatus, tilting of the shaft within the housing bore may be caused or accommodated by a bearing which enables the shaft to tilt relative to the housing. An example of such a bearing is a fulcrum bearing or focal bearing as described in U.S. Pat. No. 6,244,361 (Comeau et al) and U.S. Pat. No. 6,769,499 (Cargill et al), which are directed at “point-the-bit” types of rotary steerable drilling apparatus.